Why is the variable not added to callback_data (aiogram)?

Question

Python

There is a list with the names of the courses, I create an inline keyboard and go through all the elements of the list below. At the same time, I add the current element to the inline keyboard and also callback_data which is also equal to the current element. The problem is that this same calbback_data causes an error if you pass exactly the variable containing the current list element. If you write just some line, everything is OK, but I need a specific variable. How to be?

courses = ['first', 'second', 'и тд.']

courses_keyboard = InlineKeyboardMarkup()
for course in courses:
  courses_keyboard.add(InlineKeyboardButton(text=course, callback_data=course))

An error

raise err(cls.text or description)
aiogram.utils.exceptions.ButtonDataInvalid: Button_data_invalid

I think that there are limitations in bytes, is it possible to fix it somehow

Answer 1

Most likely the limit has been exceeded. 1-64 characters should be